The Sony Alpha 7R is a full-frame mirrorless camera with an amazing 36-megapixel image sensor. It's not quite as fast to shoot as its twin sibling, the Alpha 7, but its image quality earns it our Editors' Choice award.

By Jim FisherNon-Native LensesThe short distance between the image sensor and lens mount makes it possible to use practically any lens designed for a 35mm camera on the Alpha 7R via an adapter. Sony SLR shooters can add the LA-EA3 or LA-EA4 adapter and enjoy full autofocus compatibility with A-mount lenses from Sony and Minolta. The 7R can also accept Canon EOS lenses via an adapter by Metabones, and there are mechanical adapters out there for Nikon F, Pentax K, Leica R, and lenses from many other SLR systems. Most adapted lenses will be manual focus only, even if the lens supports autofocus. At this time the Sony/Minolta A-mount and Canon EOS lenses are the exception, and there is an autofocus adapter in development for Contax G rangefinder lenses.

But a lot of folks are going to look at the Alpha 7R as a platform for Leica M rangefinder lenses, especially considering that it's priced about $3,100 less than the least expensive full-frame digital Leica, the M-E (Typ 220). These lenses are manual focus only, so a simple mechanical adapter is all that's required to mount them. They are generally compact, and modern lenses like the Leica Summilux-M 50mm f/1.4 ASPH., are phenomenal from an optical standpoint. Rangefinder lenses are typically fairly limited in close focus, but with the Hawk Peng Macro Helicoid Adapter, which acts as a variable extension tube, the limitation is lessened. The Leica Elmarit-M 28mm f/2.8 ASPH. is able to focus as close as 0.2 meters with the adapter, versus 0.7 meter without it.

The Alpha 7R's 36-megapixel image sensor does show some issues when working with adapted lenses, notably wide-angle rangefinder glass with symmetrical designs. Even though there are microlenses along the edge of the sensor that work to improve corner performance, they are optimized for native lenses, not adapted ones. Leica has long used similar microlenses with its digital rangefinder cameras, even on the M8, the first digital M-mount camera that the company released and one that had a less-than-full-frame sensor.

The 7R shows some color shift, which presents itself as purple color cast around the edges of the frame, when paired with the Elmarit-M 28mm f/2.8 ASPH. It's not severe, but it's noticeable, and it's absent when the lens is paired with the Alpha 7 or the M (Typ 240). In addition to the color shift, there's noticeable lack of sharpness at the edges of the frame at f/2.8. Imatest shows that the lens only manages a murky 462 lines there, versus a more respectable 1,347 when paired with the Leica M.

The high-resolution sensor is likely to blame for the excessive color shift, as the 24-megapixel APS-C NEX-7 showed similar issues with wide-angle lenses. I also looked at the Voigtlander Super-Wide Heliar 15mm f/4.5 Apsherical on the 7R. It's one of the widest rangefinder lenses available, and although I only had the older Leica Thread Mount version on hand, it is optically identical to the newer M-mount version. The edges and corners are blurry at f/4.5 when paired with the 7R, and the color shift is quite severe. The 15mm is a tricky lens, it shows a color cast at the edges of the frame when paired with the Leica M. The Alpha 7 didn't show any shift with the lens, but it also struggled with sharpness at the edges and corners of the frame.

What the Elmarit-M 28mm ASPH. and the Voigtlander Super-Wide Heliar 15mm have in common is a symmetrical design. Wide-angle SLR lenses, like the Pentax SMC FA 31mm f/1.8 Limited typically employ retrofocus designs—in very basic terms a reverse telephoto—and perform much better on the A7 and A7R. But even that lens showed some edge softness on the Alpha 7R when compared with the Leica M. At f/1.8 the edges showed 1,281 lines on the Alpha 7R, 1,425 lines on the 7, and 1,560 lines on the M. Edges improve as you stop down, regardless of the camera body used, and by f/4 it's an impressive performer on all three cameras, but the Leica still wins in terms of edge-to-edge sharpness.

The Leica M enjoys one more advantage over the Alpha 7R and 7, but whether it's worth the premium price is up to you. When shooting with rangefinder lenses, the optical viewfinder and bright patch deliver a quicker manual focus experience than the Alpha 7R's OLED EVF is able to. I'm able to get sharp, in-focus shots with a 50mm f/1.4 and the Leica M rather quickly, but to do the same on the 7R I really had to use the magnification function. By default that's C1 on the top plate when using a manual focus lens, and it brings up a 7x view of the frame in the eyepiece or on the rear LCD. Focus peaking, which highlights in-focus areas of the frame, is available for working more quickly, but I found that I had to stop a 50mm lens down to about f/4 before the peaking did the job on its own. When working slowly the magnification is extremely precise, but for quick shots I still prefer an optical rangefinder. Granted, there are caveats to that—a rangefinder lens and camera need to be properly calibrated to really nail focus; if your M lens and camera aren't quite matched properly you'll never get an in-focus shot, but that's been the nature of rangefinder cameras since their inception.

Native lenses are much better performers. The two ZE Carl Zeiss prime lenses, a 35mm f/2.8 and 55mm f/1.8, are impressively sharp from edge to edge on both the Alpha 7 and 7R.

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